<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="">
    <div>
        <input type="text" placeholder="请输入账号" value="admin" >
        <input type="password" placeholder="请输入密码">
        <button onclick="fun()">登录</button>
    </div>
</form>

</body>
<script>
    function fun(){
        alert("hello");
    }
</script>
</html>